1. Field of the Invention
This invention relates to a suspension system for a row crop planter unit and more particularly to a suspension system preferably in the form of a coil-over shock absorber which is operatively connected to the supporting frame of the planter unit and to the parallel arm linkage of the row crop planter unit to reduce row unit bounce (R.U.B.).
2. Description of the Related Art
Many types of suspension systems or mounting systems for row crop planter units have been previously provided. In most instances, the row crop planter units are connected to a transversely extending toolbar in a horizontally spaced-apart manner for single row planting or in a horizontally spaced-apart and staggered or offset manner for twin row planting. The toolbar is normally wheel supported or three-point hitch supported and is pulled through a field by a prime mover such as a tractor or the like. Each of the planter units is normally connected to the toolbar by means of a parallel arm linkage so that the planter units may vertically move with respect to the toolbar. As the planter is pulled through the field, the planter units tend to bounce upwardly and downwardly due to encountering uneven terrain. If the planter unit does objectionably bounce, the seed spacing and seed depth of the planter unit will not be proper. Seed spacing is extremely important in planting operations wherein single rows are planted, and is even more important when the row crops are being planted in twin rows.
One prior art method of attempting to reduce the row unit bounce is to utilize coil springs which interconnect the upper and lower parallel arms of each of the parallel arm linkages. See, for example, U.S. Pat. No. 5,709,271 and published application No. 2006/0213407 A1. The coil springs of the prior art do exert a certain amount of down pressure on the planter unit and do reduce row unit bounce to some degree. However, it has been found that the coil spring arrangements commonly found in the prior art do not satisfactorily reduce row unit bounce thereby resulting in improper seed spacing and seed depth.